Abstract
Stretch-activated channels (SACs) have been implicated in the control of epithelial cell volume. Such channels are generally sensitive to the trivalent lanthanide, gadolinium (Gd3+). In this study, using Gd3+ sensitivity and volume activation as indices, we have looked for ionic currents attributable to SACs using the wholecell-patch clamp technique in freshly isolated proximal tubule cells of the frog. Hypotonic shock caused a reversible increase in whole-cell conductance, which was inhibited by Gd3+. In conjunction with this increase in conductance, cell length (measured using an optical technique) also increased. We observed two types of volume and Gd3+-sensitive currents: voltage-dependentI VD and voltage-independent IVI. IVD was found in all cells, activated by depolarisation and hypotonic shock, and was inhibited reversibly by 10 μM Gd3+. The conductance did not discriminate between Na+ and K+ but was slightly anion-selective and was Ca2+-permeable.I VI was observed in only 50% of cells and was also inhibited by Gd3+. Although the inhibition was irreversible, it was dose-dependent, suggesting a specific effect of Gd3+ onI VI. Cells that showed IVI had a significantly higher conductance than those that did not (38.7±4.4,n=20, and 20.5±0.7,n=15, μS · cm−2 respectively). In contrast toI VD,I VI was mildly cation-selective, Ca2+-permeable, and also selective for Na+ over K+. As withI VD, volume-induced increases inI VI were inhibited by Gd3+. Both of these currents are activated during hypotonic shock and may be involved in volume-regulatory processes in frog proximal cells.
Similar content being viewed by others
References
Boron WF, Boulpaep EL (1983) Intracellular pH regulation in the renal proximal tubule of the salamander. Basolateral HCO −3 transport. J Gen Physiol 81:53–94
Busch AE, Maylie J (1993) MinK channels: a minimal channel protein with maximal impact. Cell Physiol Biochem 3:270–276
Christensen O (1987) Mediation of cell volume regulation by calcium influx through stretch-activated channels. Nature 330:66–68
Filipovic D, Sackin H (1991) A calcium-permeable stretch-activated cation channel in renal proximal tubule. Am J Physiol 260:F119-F129
Filipovic D, Sackin H (1992) Stretch- and volume-activated channels in isolated proximal tubule cells. Am J Physiol 262:F857-F870
Guharay F, Sachs F (1984) Stretch-activated single ion channel currents in tissue-cultured embryonic chick skeletal muscle. J Physiol (Lond) 352:685–701
Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch clamp techniques for high resolution current recording from cells and cell free membrane patches. Pflügers Arch 391:85–100
Hille B (1992) Ionic channels in excitable membranes, 2nd edn. Sinauer Associates, Mass.
Hoffmann EK, Simonsen LO (1989) Membrane mechanisms in volume and pH regulation in vertebrate cells. Physiol Rev 69:315–382
Hunter M (1989) Isolation of single proximal cells from frog kidneys. J Physiol (Lond) 416:13P
Hunter M (1990) Stretch-activated channels in the basolateral membrane of single proximal cells of frog kidney. Pflügers Arch 416:448–453
Kawahara K (1990) A stretch-activated K+ channel in the basolateral membrane ofXenopus kidney proximal tubule cells. Pflügers Arch 415:624–629
Kirk KL, DiBona DR, Schafer JA (1987) Regulatory volume decrease in perfused proximal nephron: evidence for a dum** of cell potassium. Am J Physiol 252:F933-F942
Kirk KL, Schafer JA, DiBona DR (1987) Cell volume regulation in rabbit proximal straight tubule perfused in vitro. Am J Physiol 252:F922-F932
Lang F, Oberleithner H, Giebisch G (1986) Electrophysiological heterogeneity of proximal convoluted tubules inAmphiuma kidney. Am J Physiol 251:F1063-F1072
Lewis CA (1979) Ion-concentration dependence of the reversal potential and the single channel conductance of ion channels at the frog neuromuscular junction. J Physiol (Lond) 286:417–445
Lopes AG, Guggino WB (1987) Volume regulation in the early proximal tubule of theNecturus kidney. J Membr Biol 97:117–125
Matsumura Y, Cohen B, Guggino WB, Giebisch G (1984) Electrical effects of potassium and bicarbonate on proximal tubule cells ofNecturus. J Membr Biol 79:145–152
Robson L, Hunter M (1994) Volume regulatory responses in frog isolated proximal cells. Pflügers Arch 428:60–68
Sackin H (1987) Stretch-activated potassium channels in renal proximal tubule. Am J Physiol 253:F1253-F1262
Sackin H, Gu X (1993) A voltage-activated hydrogen ion conductance in proximal tubule (abstract). J Am Soc Nephrol 4:878
Thomas RC (1988) Changes in the surface pH of voltage clamped snail neurones apparently caused by H+ fluxes through a channel. J Physiol (Lond) 398:313–327
Ubl J, Murer H, Kolb HA (1988) Ion channels activated by osmotic and mechanical stress in membranes of opossum kidney cells. J Membr Biol 104:223–232
Volkl H, Lang F (1988) Ionic requirements for regulatory cell volume decrease in renal straight tubules (proximal). Pflügers Arch 412:1–6
Welling PA, Linshaw MA (1988) Importance of anion in hypotonic volume regulation in rabbit straight tubule. Am J Physiol 255:F853-F860
Welling PA, O'Neil RG (1990) Cell swelling activates basolateral membrane Cl− and K+ conductances in rabbit proximal tubule. Am J Physiol 258:F951-F962
Welling PA, Linshaw MA, Sullivan LP (1985) Effect of Ba2+ on cell volume regulation in rabbit proximal straight tubules. Am J Physiol 249:F20-F27
Yang X, Sachs F (1989) Block of stretch-activated ion channels inXenopus oocytes by gadolinium and calcium ions. Science 243:1068–1071
Author information
Authors and Affiliations
Additional information
This work was supported by the Wellcome Trust
Rights and permissions
About this article
Cite this article
Robson, L., Hunter, M. Volume-activated, gadolinium-sensitive whole-cell currents in single proximal cells of frog kidney. Pflugers Arch. 429, 98–106 (1994). https://doi.org/10.1007/BF02584035
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02584035